Device and method for producing a defined value for the control of a drive

ABSTRACT

An apparatus and a method for generating a set-point value for triggering at least one drive mechanism, in particular for a machine tool, are proposed, wherein, in a parts program ( 20 ) for describing a path of motion of a tool ( 12 ) movable by the at least one drive mechanism ( 18 ), at least two parts program positions (X 1 , Y 1 , Z 1 ; X 2 , Y 2 , Z 2 ; X 3 , Y 3 , Z 3 ) are stored in memory. A controller ( 18 ) which from the parts program ( 20 ) ascertains at least one drive mechanism set-point value (VA(S)) for triggering the drive mechanism ( 18 ). Means ( 18 ) are provided for ascertaining a distance (S) that is located between the at least two parts program positions (X 1 , Y 1 , Z 1 ; X 3 , Y 3 , Z 3 ) and for generating a drive mechanism set-point value (VA(S)) as a function of the distance (S) and of at least one parts program parameter (V 1 , V 2 ).

BACKGROUND OF THE INVENTION

The invention is based on an apparatus and a method for generating aset-point value for triggering at least one drive mechanism, inparticular for machine tools. In conventional machine tool controllers,movement specifications can be stored in memory inside a so-called partsprogram in the form of a succession of support points. In order to takecertain technical conditions into account, dynamic conditions are storedin memory in, the parts program in the form of feed values. Particularlyin the case of a path of motion whose feed values fluctuate severely,ramp-like speed courses can become established, since as a rule, thecontroller imposes a train of set-point values on the drive mechanism inorder to reach the next programmed feed value with maximum acceleration.The discontinuous speed courses that result under some circumstancesmake high demands on the machine mechanics. These have an adverse effecton the machining quality.

SUMMARY OF THE INVENTION

The object of the invention is to specify suitable set-point values tothe drive mechanism of a machine tool so as to achieve a uniform courseof speed and/or acceleration. This object is attained with thecharacteristics of the bodies of the independent claims.

ADVANTAGES OF THE INVENTION

The apparatus and method according to the invention for generating aset-point value for triggering at least one drive mechanism, inparticular for a machine tool, includes a parts program or a comparablearrangement for describing a path of motion of a tool that is movable bythe drive mechanism. The parts program includes at least two partsprogram positions with an associated parts program parameter, such asthe feed. From the parts program, the controller ascertains a train ofset-point values for triggering the drive mechanism. Means are providedfor ascertaining a distance that is located between the at least twoparts program positions and for generating the train of set-point valuesas a function of the distance and of the parts program parameter.

Including the distance to be traversed between two position valuespermits a uniform, continuous specification of the drive mechanismset-point value. By ascertaining the distance still to be traveled, thetotal (future) path of motion sequence is incorporated into theset-point value specification. As a result, fast, continuous machiningof workpieces can be achieved. Gentle speed or acceleration transitionscan be attained even when the motion sequences are fluctuating severely.In addition, the apparatus according to the invention enables simpleprogramming of a parts program when the speed specifications are varyingsharply. Only two position values have to be programmed with theassociated motion values (speed or acceleration). On its own, thecontroller ascertains the distance located between the two positionvalves and from that derives a continuous course of the drive mechanismset-point values as a function of the change in the two parts programparameters stored in memory. A path of motion with feed values that varymonotonously need not be specified on the basis of individual NC sets;merely programming the starting and ending feed values as parts programparameters suffices.

In an expedient refinement, the at least two parts program positions, towhich respective beginning and ending parts program motion values areassigned, are identified in a certain way in order to cause thecontroller to ascertain the distance between precisely these two partsprogram positions. The user can easily alternate between theconventional specification of a drive mechanism set-point value or thataccording to the invention, depending on the kind of machining desired.

Another advantageous feature provides that the drive mechanism set-pointvalues be interpolated linearly between the parts program parameterswith regard to the speed.

Further expedient refinements will become apparent from other dependentclaims and from the description.

DRAWING

One exemplary embodiment is shown in the drawing and explained infurther detail in the ensuing description.

FIG. 1 is a block circuit diagram;

FIGS. 2, 3 a, 3 b, and 5 show typical set-point value courses;

FIG. 4 shows a parts program; and

FIG. 6 is flowchart for the apparatus and the method according to theinvention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

A workpiece 10 is machined by a tool 12, which is driven at least in thex direction by a drive mechanism 16. The drive mechanism 16 receivesset-point values from a controller 18, which processes data of a partsprogram 20 accordingly. FIG. 2 shows a typical ramplike feed course V ofthe prior art.

FIGS. 3a, 3 b show a course of feed or acceleration of the kind thatresults in the apparatus and method of the invention. In the partsprogram 20 in FIG. 4, three NC data sets are shown as examples. A startcommand designated Gxx tells the controller 18 that the set-point valuespecification according to the invention should be used to begin with.In this first NC set, first parts program positions X1, Y1, Z1 are alsostored in memory along with an associated first parts program parameterV1. As the parts program parameter, in the exemplary embodiment, theprogrammed feed V1 is used, hereinafter called the parts program feed.In the second data set, a second parts program position X2, Y2, Z2,which is to be approached, is indicated. The third NC data set ispreceded by an end command Gxy, along with a third parts programposition X3, Y3, Z3 with a second parts program parameter V2,hereinafter called the second parts program feed V2. The associatedmotion diagram is shown in FIG. 5. The plus signs located on thestraight line represent the distance-dependent drive mechanism set-pointvalues VA(S) ascertained by the controller 18. These are speed oracceleration values, ascertained according to the invention, which canoptionally be made available to the drive mechanism 16 as positionset-point values by integration.

In a conventional drive mechanism set-point value specification, a feedcourse as shown in FIG. 2 results. Conventionally, each parts programposition X1, X2, X3 in the parts program 20 is assigned the respectiveparts program feed V1, V2, V3. In the first parts program position, theconventional controller specifies a maximum acceleration as a set-pointvalue to the drive mechanism 16 for reaching the programmed partsprogram feed V2 no later than by the second parts program position X2.This second parts program feed V2 is as a rule already reached markedlybefore the second parts program position X2, resulting in the ramplikecourse shown, which leads to the speed course shown.

In the apparatus and the method according to the invention, conversely,continuous motion courses are achieved in a targeted way, as shown inFIGS. 3a, 3 b. How this course of motion comes about will be explainedin terms of the exemplary embodiment in conjunction with FIGS. 4 and 5.The beginning of a portion in a parts program 20 that is distinguishedby severely fluctuating feed courses is marked by the start command Gxx.The first parts program position X1, Y1, Z1 is reached with the firstparts program feed V1. If no first parts program feed V1 has beenprogrammed in the data set, then the controller 18 makes use of the mostrecent parts program feed in the NC program. By means of the startcommand Gxx, the set-point value specification according to theinvention is initiated. If the controller 18 recognizes the startcommand Gxx, which is step 103, then by integration it ascertains thedistance S which is traversed, beginning at the first parts programposition X1 marked by the start command Gxx, through the further partsprogram position X2, to the third parts program position X3 marked bythe end command Gxy. The controller 18 first calculates the distance Sto the second parts program position X2, which can be immediatelyfollowed by still other intermediate positions. The distance S to thenext intermediate position X to be approached is determined, which isstep 105, until such time as the end command Gxy is recognized, which isstep 107. The resultant length of the distance at the third partsprogram position X3 identified by the end command Gxy is stored inmemory as the maximum distance Smax for the further determination of thedrive mechanism set-point values VA; this is step 109. The second partsprogram feed V2 to be reached is stored in memory in this third NC set.The controller 18 recognizes that increasing the feed from V1 to V2 canbe reached within the ascertained distance Smax.

The specification of the drive mechanism set-point values VA(S), whichin the exemplary embodiment is the set-point speed of the drivemechanism, is accomplished as a function of the distance S. In FIG. 5, alinear increase in the feed is contemplated. The drive mechanismset-point values can be described by a known linear equation taking thefollowing form:

VA(S)=(V 2−V 1)*(S:Smax)+V 1.

With this equation, the result can for instance be the drive mechanismset-point value course VA marked by plus signs in FIG. 5, if the drivemechanism set-point values VA(S) are specified discretely with the samedistance spacing ΔS. The drive mechanism set-point values VA are thusdistinguished by a uniform course, resulting in a path of motion asshown in FIGS. 3a, 3 b.

In terms of usage, numerous modifications are conceivable. Instead of alinear speed transition as described above, the drive mechanismset-point values VA could in principle be described by arbitrarymathematical functions. A function shown in dot-dashed lines in FIG. 5assures a smooth transition between the two feed values V1, V2, withoutany kinks in the course of acceleration.

The calculation according to the invention of the drive mechanismset-point value specification could also be employed if instead of thefeed values V1, V2, corresponding speed changes have to be traversedwithout jerking.

What is claimed is:
 1. An apparatus for generating a set-point value fortriggering at least one drive mechanism (16) for a tool (12), saidapparatus comprising a parts program (20) comprising means fordetermining a path of motion of the tool (12); and a controller (18) forcontrolling said at least one driver mechanism (16) of said tool;wherein at least two parts program positions (X1, Y1, Z1; X2, Y2, Z2;X3, Y3, Z3) stored in memory, at least one (X1, Y1, Z1) of said at leasttwo parts program positions is identified with a start command (Gxx) andat least one other (X3, Y3, Z3) of said at least two parts programpositions is identified with an end command (Gxy); and wherein saidcontroller (18) includes means for ascertaining a distance (S) betweensaid at least one parts program position and said least one other partsprogram position (X1, Y1, Z1; X3, Y3, Z3) identified by the startcommand (Gxx) and the end command (Gxy) respectively, and means forgenerating a drive mechanism set-point value (VA(S)) as a function ofsaid distance (S) and of at least one parts program parameter (V1, V2).2. The apparatus as defined in claim 1, wherein said drive mechanismset-point value (VA(S)) varies linearly with time.
 3. The apparatus asdefined in claim 1 or 2, wherein said drive mechanism set-point value(VA(S)) is a speed or acceleration value.
 4. The apparatus as defined inclaim 1, further comprising integrating said drive mechanism set-pointvalue (VA(S)) to obtain an integrated value and feeding said integratedvalue to said at least one drive mechanism as a set-point variable. 5.The apparatus as defined in claim 1, wherein said at least one partsprogram parameter (V1, V2) is a programmed feed.
 6. The apparatus asdefined in claim 1, further comprising a machine tool including said atleast one drive mechanism (16) and said tool (12) driven by said atleast one drive mechanism (16).
 7. A method for generating a set-pointvalue for triggering at least one drive mechanism (16) for a tool (12)by means of a controller (18), said method comprising the steps of: a)providing a parts program for determining a path of motion of the tool(12); b) storing at least two parts program positions (X1, Y1, Z1; X2,Y2, Z2; X3, Y3, Z3) in memory; c) ascertaining by means of thecontroller (18) a distance (S) between one of said parts programpositions and another of said parts program positions identified by astart command (Gxx) and an end command (Gxy) respectively; and d)generating a drive mechanism set-point value (VA(S)) as a function ofsaid distance (S) and of at least one parts program parameter (V1, V2)by means of the controller (18).